Ignition apparatus for internal combustion engines



8- 1940- I v T. F. ROBINSON v 2,212,404

IGNITION APPARATUS FOR INTERNAL COMBUSTION ENGINES Fi'led Nov. 12, 19382 Sheets-Sheet 1 Figi Invent 0 Thomas F. Robinson,

His AtboT-neg.

Au 20; V T. EROBINSON I 5 mnrrlfou- APPARATUS FOR INTERNAL cousus'rzoumamas V Filed Nov. 12, 1939 2 Shqets-Sheet 2 vaLTs M :Th mas Robinson,

His Hoof-neg.

Patented Aug. 20, 1940 UNITED STATES PATENT OFFICE I IGNITION APPARATUSFOR INTERNAL COMBUSTION ENGINES ration of New York Application November12, 1938, Serial No. 240,187

' In Great Britain November 11, 1937 g Claims.

(Granted under the provisions of sec. 14, act of March 2, 1927; 357 0.G. 5)

This invention relates to ignition apparatus for internal combustionengines. The usual type of magneto-electric machine commonly used forigition purposes does not give satisfactory perform- 5 ance at highspeeds due partly to the short time available for building up the fluxin the armature core and partly to poor contact breaker operation whichis the result of a large open period cam design necessitated by the timeof the flux building'up just referred to.

The object of the present invention'is to provide an improved system ofignitionparticularly suitable for high speed operation.

16 According to the present invention we provide an alternator as asource of electromotive force which charges a condenser on eachsuccessive half voltage wave by means of a contact breaker such as amechanical rectifier and subsequently discharge the condenser throughthe primary of 5 an ignition coil by means of a contact maker in orderto produce a high tension electromotive force inthe ignition coilsecondary. With such an arrangement the time necessary for fluxbuilding-up does not arise and the cam required for the operation of thecontact mechanisms can be designed for nearly equal periods thusreducing the contact flinging which takes place with an unequal periodcam due to rapid acceleration imparted to the lever.

The accompanying drawings illustrate this invention. Figs. 1, 2 and 3show diagrammatic ignition circuits, Figs. 4 and 5 are curves showingthe points of ignition, and Fig. 6 is a modified form of the circuitshown in Fig. 1.

Referring to Fig. 1, A is a source of alternating current electric powersupply, such as a small alternator driven from the internal combustionengine and connected to the condenser C through a contact breaker Bloperated by a cam so arranged on the alternator shaft that the contactsbreak the circuit on the rising portion of the alternator voltage waveso charging the condenser to the instantaneous voltage value v of thewave at the moment of breaking the circuit.

The electrostatic energy ayailable in the condenser at this instant isequal to Cv joules. The condenser is then discharged by means of contactbreaker B2 through the primary P of an induction coil or an ignitiontransformer T, the

resultant high tension voltage which is developed in the secondary Sbeing distributed by the usual type of distributor D to the appropriateplugs X in the engine cylinders. This system operates on both thepositive and the negative half cycles of the alternator voltage wavegiving in effect two sparks per pair of poles per revolution of thealternator. In the circuit arrangement shown in Fig. l the contactpoints of both contact mechanisms are at the instant of "break in thecase of BI and "make" in the case of B2 at a potential relative to earthand require to be insulated. From a design point of view this is in somecases not convenient or desirable and the arrangements shown in Figs. 2or 3 may be adopted as an alternative. In Fig. 2 one of the contacts of10 contact breaker BI is connected to earth at E. y In this figure itwill be noted that the contact breakers BI and B2 are combined so thatthey can be manufactured as a single unit the contact lever carrying twocontacts one for break at BI 15 and the other for make at B2.

In Fig. 3 the circuit is connected to earth between the alternator andthe contact breaker Bl.

, As an engine requires an ignition system which so will operate over aconsiderable timing range this is obtained by the present invention asfollows:

For a retarded contact timing, which is usually required at low speedsfor starting purposes, the 25 contacts would be arranged to operate onthe crest of the voltage wave, as shown in Fig. 4, as at low speeds thevoltage of the alternator will be low and the peak voltage must beutilised to obtain the best results. increases the voltage increases andas an advanced timing position is only required at medium and highspeeds, this timing advance can only be obtained without loss of therequisite condenser voltage by operating the contacts at a 3| positionon the voltage wave prior to the peak position as shown in Fig. 5.

As the high tension requirements of an engine are more or less constantover the whole speed range, it is unnecessary for the alternator to de-40 velop a greater voltage than that required for the establishment ofsumcient electrostatic energy in the condenser C for the production ofthe requisite high tension voltage from the secondary of the ignitiontransformer. If it is desired to limit I the output, a second condenserCl, shown in Figs.

1, 2 and 3 may be connected across the alternator terminals to limit itsoutput voltage at high speeds. It is also desirable to limit thealternator voltage at medium and high speeds as immediately contacts Blopen a considerable potential difference exists between them This is duefirstly to the removal of the condenser load thereby causing animmediate rise in the alternator voltage, and secondly, with the systemI As the alternator speed 81) operating in the advance timing positionas shown in Fig. 4 to the natural progression of the voltage wave fromits instantaneous value at BI when the contacts open to a higher valueat a very short time interval later.

In order to limit this voltage rise across the contacts BI as well as tolimit the voltage of the alternator, a condenser C2 is connected asshown in Fig. 6 across these contacts. Other voltage limiting means maybe provided for obtaining the requisite speed-voltage characteristics ofthe alternator.

At very low speeds the alternator may be insuflicient to provide thenecessary energy in the condenser C for the production of the requisitehigh tension voltage. The required energy can be provided by connectingin parallel with the condenser C an additional condenser C3 (Fig.,

6) of suitable value. As this additional condenser will impair theperformance at high speeds its use is confined to engine starting andlow. speed running purposes. A switch Sw is provided, which may bemanually or centrifugally operated, so that the condenser C3 may be cutout of circuit when the speed of the alternator increases above apredetermined value. The provision of this additional condenser for slowspeed running renders the system capable of producing satisfactoryignition over a very wide range.

It will be understood that the condenser C2 and condenser C3 with itscontrolling switch may be added to the modifications illustrated inFigs. 2 and 3 of the drawings when condenser Cl is omitted.

Iclaim:

1. The method of providing ignition sparks in the cylinders of internalcombustion engines which consists in the employment of an alternator asa source of current and causing each half of the voltage wave to chargea condenser which is discharged through a primary winding of an ignitioncoil thereby producing a high tension electromotive force in a secondarywinding of the coil which is distributed through a distributor to anappropriate plug in the engine cylinders.

2. An ignition system including a source of alternating current electricpower supply, a condenser, an induction coil having a primary windingand a secondary winding, and means for connecting said condenseralternately across said source of alternating current electrical powersupply for at least a part of each half wave of voltage to charge saidcondenser and across said primary winding to discharge said condensertherethrough and induce an electrical potential in said secondarywinding.

3. An ignition system including a source of alternating current electricpower supply, a condenser, an induction coil having a primary windingand a secondary winding, means for connecting and disconnecting saidcondenser across said source of alternating current electric power supply and for providing said connection for at least a part of each halfwave oi! voltage to charge said condenser, and means for connecting anddisconnecting said condenser across said primary winding and forproviding said connection for at least a part of the time-said condenseris not connected across said alternating current source of electricalpower supply to discharge said cpndenser through said primary winding.

4. An ignition system including a source of alternating current electricpower supply, a condenser, an induction coil having a primary windingand a secondary winding, means including a circuit breaker forconnecting and disconnecting said condenser across said source ofalternating current electric power supply and for providing saidconnection for at least a part of each half wave of voltage to chargesaid condenser, means including a second circuit breaker for connectingand disconnecting said condenser across said primary winding and forproviding said connection for a least a part of the time said condenseris not. connected across said alternating current source of electricalpower supply to discharge said condenser through said. primary winding,and a second condenser connected in parallel with said first-mentionedcircuit breaker to limit the voltage of the alternating current sourceof electrical power supply thereacross.

5. An ignition system including an alternator providing a source ofalternating current electric power supply, a condenser, an inductioncoil having a primary winding and a secondary winding means forconnecting and disconnecting said condenser across said source ofalternating current electric power supply and for providing saidconnection for at least a part of each half wave of voltage to chargesaid condenser, means for connecting and disconnecting said condenseracross said primary winding and for providing said connection for atleast a part of the time said condenser is not connected acrosssaid-alternating current source of electrical power supply to dischargesaid condenser through said primary winding, a second condenser, meansfor connecting said second condenser in parallel cirnator.

THOMAS FREDERIC ROBINSON.

